function start ()
{
	var canvas = document.getElementById("glcanvas");
	initWebGL(canvas);
	if(gl)
	{
		gl.clearColor(0.0, 0.0, 0.0, 0.0);
		gl.enable(gl.DEPTH_TEST);
		gl.depthFunc(gl.LEQUAL);
		gl.clear(gl.COLOR_BUFFER_BUT|gl.DEPTH_BUFFER_BIT);
	}		
}
		
function initWebGL(canvas)
{
	gl = null;
	try 
	{
		gl = canvas.getContext("webgl") || canvas.getContext("experimental-webgl");
	}
	catch(e){}
	if(!gl)
	{
		alert("unable to initialize Webgl. Your browser may not support it.");
	}
}
